Electronic flash controlling device

ABSTRACT

An electronic flash controlling device controls a flash light emitting unit that performs a main light emission and a preliminary light emission prior to the main light emission. A maximum preliminary light emission quantity setting unit sets a maximum preliminary light emission quantity for the preliminary light emission during which a smaller quantity of light is emitted than a maximum light emission quantity based upon maximum light emission quantity information regarding a total light emission quantity which the flash light emitting unit is capable of generating. A preliminary light emission executing unit engages the flash light emitting unit in the preliminary light emission by using the maximum preliminary light emission quantity set by the maximum preliminary light emission quantity setting unit as an upper limit.

INCORPORATION BY REFERENCE

[0001] The disclosure of the following priority application is hereinincorporated by reference: Japanese Patent Application No. 2001-119962filed Apr. 18, 2001

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an electronic flash controllingdevice capable of implementing optimal control on flash light emissionquantity.

[0004] 2. Description of Related Art

[0005] Devices that are employed to control the flash light emissionquantity in related art include the one disclosed in Japanese Laid-OpenPatent Publication No. H 4-182631. This electronic flash controllingdevice performs a preliminary light emission prior to the main lightemission by a flash light emitter when performing a photographingoperation with a single lens reflex camera or the like. The preliminarylight emission may be achieved by, for instance, repeatedly emitting asmall predetermined quantity of light in correspondence to the type offlash light emitter used. In this device, the maximum number of suchsmall light emissions to be performed is set in advance, in order toensure that a sufficient level of energy is left available for the mainlight emission after the preliminary light emission is implemented.

[0006] However, the flash light emitter is often exchangeable. In thedevice described above, a single value is set for the maximum number ofsmall light emissions for the preliminary light emission regardless ofthe type of flash light emitter. For this reason, the onus to be borneduring the preliminary light emission is bound to be large if a flashlight emitter with a small maximum main light emission quantity for themain light emission is mounted in the camera, which poses problems inthat the main light emission becomes disabled and in that a sufficientquantity of light is not emitted during the main light emission.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to provide an electronicflash controlling device capable of assuring the required quantity oflight to be emitted by a flash light emitter with a small maximum mainlight emission quantity during the main light emission even after apreliminary light emission.

[0008] In order to achieve the object described above, an electronicflash controlling device employed to control a flash light emitting unitthat performs a main light emission and a preliminary light emissionprior to the main light emission comprises a maximum preliminary lightemission quantity setting unit that sets a maximum preliminary lightemission quantity for the preliminary light emission during which asmaller quantity of light is emitted than a maximum light emissionquantity based upon maximum light emission quantity informationregarding a total light emission quantity which the flash light emittingunit is capable of generating; and a preliminary light emissionexecuting unit that engages the flash light emitting unit in thepreliminary light emission by using the maximum preliminary lightemission quantity set by said maximum preliminary light emissionquantity setting unit as an upper limit.

[0009] In order to achieve the object described above, an electronicflash controlling system comprises a camera main body having a maximumpreliminary light emission quantity setting unit that sets a maximumpreliminary light emission quantity for a preliminary light emissionduring which a smaller quantity of light is emitted than a maximum lightemission quantity, based upon maximum light emission quantityinformation regarding a total light emission quantity which a flashlight emitting unit is capable of generating, and a preliminary lightemission executing unit that issues an instruction to perform thepreliminary light emission to the flash light emitting unit by using themaximum preliminary light emission quantity set by said maximumpreliminary light emission quantity setting unit as an upper limit; andan electronic flash device that can be detachably mounted at said cameramain body, having said flash light emitting unit that performs a mainlight emission and the preliminary light emission prior to the mainlight emission and a preliminary light emission regulating unit thatregulates said flash light emitting unit to disallow a preliminary lightemission which results in a light emission quantity exceeding apredetermined preliminary light emission quantity even if theinstruction has been issued from said camera main body to perform thepreliminary light emission which results in the light emission quantityexceeding the predetermined preliminary light emission quantity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 schematically illustrates the optical system of a cameramounted with an electronic flash controlling device achieved in anembodiment of the present invention;

[0011]FIG. 2 is a block diagram of the structure of the electronic flashcontrolling device in the embodiment of the present invention;

[0012]FIG. 3A shows the photometering areas set in the ambient lightmetering unit of the electronic flash controlling device in theembodiment;

[0013]FIG. 3B shows that each of the photometering areas in FIG. 3A isdivided into photometering areas corresponding to three differentcolors, i.e., red, green and blue;

[0014]FIG. 4A shows areas set in the focal point detection unit in theelectronic flash controlling device in the embodiment;

[0015]FIG. 4B shows the optical system of the focal point detection unitin the electronic flash controlling device in the embodiment;

[0016]FIG. 5 shows the optical system of the flash metering unit and thearea division achieved therein in the electronic flash controllingdevice in the embodiment;

[0017]FIG. 6 illustrates in an approximation the relationship betweenthe maximum main light emission quantity GNh and the optimal upper limitQpre_max to the number of small light emissions;

[0018]FIG. 7 shows the terminals of the flash metering unit;

[0019]FIG. 8 shows a method that may be employed to set the gains at theamplifiers in the flash metering unit;

[0020]FIG. 9 shows a method that may be adopted to read out theintegrated photometering values obtained at the flash metering unit;

[0021]FIG. 10 illustrates a light emitting operation performed by theelectronic flash controlling device achieved in the embodiment;

[0022]FIG. 11 illustrates a light emitting operation performed by theelectronic flash controlling device achieved in the embodiment;

[0023]FIG. 12 schematically illustrates the relationship between thesensitivity SV of the image-capturing element and the gain;

[0024]FIG. 13 schematically illustrates the relationship between thelight emission quantity GNp1 per small light emission and the gain;

[0025]FIG. 14 schematically illustrates the relationship between thedistance and the gain;

[0026]FIG. 15 schematically illustrates the relationship between theaperture value AV and the gain;

[0027]FIG. 16 schematically illustrates the relationship between thebrightness BV and the gain;

[0028]FIG. 17 is a flowchart of the processing executed in conformanceto the electronic flash control program in the camera microcomputer inthe electronic flash controlling device achieved in an embodiment of thepresent invention;

[0029]FIG. 18 is a flowchart of the control procedure implemented duringthe preliminary light emission in the electronic flash controllingdevice in the embodiment;

[0030]FIG. 19 presents a flowchart of the c ontrol procedure implementedduring the ma in light emission by the electronic flash controllingdevice in the embodiment; and

[0031]FIG. 20 schematically illustrates the relationship between thereflectance and a weighting value RefG(i);

[0032]FIG. 21 schematically illustrates the relationship between thereflectance and the main light emission quantity correction value ΔY;

[0033]FIG. 22 is a flowchart of the control procedure implemented duringthe preliminary light emission by the electronic flash microcomputer inthe electronic flash controlling device achieved in a variation of theembodiment of present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] The electronic flash controlling device according to the presentinvention sets the maximum light emission quantity for a preliminarylight emission preceding the main light emission based upon the maximummain light emission quantity of the electronic flash device. Thefollowing is a detailed explanation given in reference to the drawings.

[0035]FIG. 1 schematically illustrates the optical system of a cameramounted with the electronic flash controlling device achieved in anembodiment of the present invention. The explanation is given on anexample in which the electronic flash controlling device in theembodiment of the present invention is adopted in an digital stillcamera.

[0036] A light flux (ambient light) having passed through a photographiclens 1 is reflected at a main mirror 2 and forms an image on a diffusingscreen 3. Then, it travels through a condenser lens 4, a pentaprism 5and an eyepiece lens 6 to reach the photographer's eye.

[0037] Part of the light flux diffused at the diffusing screen 3re-forms an image on an ambient light metering unit 21 through thecondenser lens 4, the pentaprism 5, a photometering prism 7 and aphotometering lens 8.

[0038] The main mirror 2 is a half mirror which allows part of the lightto be transmitted. The light flux that has been transmitted through themain mirror 2 instead of having been reflected at the main mirror 2 isbent in the downward direction in FIG. 1 at a sub mirror 13 to be guidedto a focal point detection unit 23.

[0039] When a shutter release switch 26 in FIG. 2 is operated, anaperture 10 is constricted to a predetermined value and, at the sametime, the main mirror 2 swings upward. Subsequently, a preliminary lightemission is performed at a flash light emitting unit 36 included in anelectronic flash device 53 detachably mounted at the camera body 51, inorder to ascertain the photographic field state. At this time, a portionof the light reflected from the photographic field is reflected on ashutter 11 and is guided to a flash metering unit 22 through a flashcontrol lens 14. The flash light emitting unit 36 performs a main lightemission after the preliminary light emission. The shutter 11 is openedduring this process so that the reflected light from the photographicfield having passed through the photographic lens 1 forms an image onthe light-receiving surface of an image-capturing element 12, which maybe constituted of, for instance, a CCD.

[0040] The ambient light metering unit 21 is constituted of alight-receiving element such as a CCD (charge coupled device) and thelike. The ambient light metering unit 21 assumes a structure that allowsit to perform a photometering operation at 330 small areas, forinstance, achieved by dividing essentially the entire plane of thephotographic field into 22 (across)×15 (down) areas, as illustrated inFIG. 3A, to output the photometering values corresponding to theindividual areas. As shown in FIG. 3B, each photometering area includesphotometering cells corresponding to three different colors, i.e., R(red), G (green) and B (blue), so as to enable a photometering operationto be performed by separating the light into the three different colors.In addition, the ambient light metering unit 21 is capable of outputtingaveraged photometering values corresponding to areas B1˜B5 obtained bygrouping the photometering areas in conformance to the area division atthe flash metering unit 22, as shown in FIG. 3A. The ambient lightmetering unit 21 outputs the photometering values corresponding to theindividual areas to a camera microcomputer 30 to be detailed later.

[0041]FIG. 4A shows focal point detection areas F1˜F5 in thephotographic field and FIG. 4B shows the optical system of the focalpoint detection unit 23. As shown in FIG. 4B, the focal point detectionunit 23 comprises the photographic lens 1, a field mask 16, a field lens19, a separator lens 20, an autofocus sensor 34 and the like. The focalpoint detection unit 23 detects the focusing states in the focal pointdetection areas F1˜F5 of the photographic field shown in FIG. 4A througha phase difference detection method or the like. The focal pointdetection unit 23 drives the photographic lens 1 until a focused stateis achieved in one of the areas F1˜F5. The focal point detection areawhere a focused state is to be achieved is selected manually by thephotographer, or selected through a closest subject distance selectionin the camera or the like.

[0042] The flash metering unit 22 is constituted of a light-receivingelement such as a silicon photodiode (SPD), capacitors that store thephotocurrents from the SPD, amplifiers (not shown) and the like. Asshown in FIG. 5, the subject image formed by the light having enteredthe shutter surface 11 is reformed at the light-receiving element of theflash metering unit 22 via the flash control lens 14, which includesthree lenses. The light-receiving element of the flash metering unit 22is divided into 5 areas S1˜S5 in correspondence to the areas B1˜B5obtained by dividing the photographic field as shown in FIG. 3A. Theflash metering unit 22 individually stores the charges resulting fromthe photoelectric conversion performed in the areas S1˜S5 and theamplification at the amplifiers into the capacitors corresponding to theareas S1˜S5. It is to be noted that the areas S1˜S5 correspond to theareas B1˜B5 at the ambient light metering unit 21 shown in FIG. 3A. Amore detailed explanation is to be given later on the flash meteringunit 22 in reference to FIG. 7.

[0043] Next, in reference to FIG. 2, the basic operation of a cameramounted with the electronic flash controlling device according to thepresent invention is explained. FIG. 2 is a block diagram showing thestructure of the electronic flash controlling device achieved in theembodiment of the present invention. The basic operation described belowis controlled by the camera microcomputer 30 at a camera main body 51.It is to be noted that the camera microcomputer 30, a lens microcomputer33 at a lens main body 52 and an electronic flash microcomputer 35 at anelectronic flash device 53 are each constituted of a microprocessor. Thelens microcomputer 33 and the electronic flash microcomputer 35 areelectrically connected with the camera microcomputer 30.

[0044] (1) Photometering exposure control

[0045] The ambient light metering unit 21 described above outputs thephotometering values from the photographic field divided into the 330small areas to the camera microcomputer 30. Lens information such as theF-number, the focal length and the exit pupil position with regard tothe photographic lens 1 stored in the lens microcomputer 33 is providedto the camera microcomputer 30.

[0046] The camera microcomputer 30 calculates the correct exposure valuefor ambient light exposure based upon the photometering values providedby the ambient light metering unit 21, the lens information provided bythe lens microcomputer 33, information indicating the sensitivity of theimage-capturing element 12 provided from a sensitivity setting unit 25and the like. The camera microcomputer 30 determines an aperture valueand a shutter speed based upon the correct exposure value and outputsthe individual values to an aperture control unit 27 and the shutter 11.The aperture control unit 27 drives the aperture 10 at the lens mainbody 52 in conformance to the input value. An actuator (not shown) atthe shutter 11 adjusts the shutter speed in conformance to the valueinput thereto.

[0047] It is to be noted that the aperture control unit 27 implementsconstrict/reset control on the aperture 10 in response to a shutterrelease signal from the shutter release switch 26, i.e., in response toa full press operation of the shutter release switch 26.

[0048] (2) Autofocus control

[0049] The focal point detection unit 23 detects the focusing states inthe five focal point detection areas F1˜F5 shown in FIG. 4A. The focusinformation obtained through the detection performed by the focal pointdetection unit 23 is provided to the camera microcomputer 30.

[0050] The camera microcomputer 30 calculates a lens drive quantity soas to achieve a focused state in a given focal point detection areabased upon the input focus information and outputs the calculated lensdrive quantity to a lens drive unit 24. The lens drive unit 24 drives alens optical system 31 at the lens main body 52 so as to achieve afocused state in correspondence to the input lens drive quantity. Atthis time, the distance over which the lens optical system 31 has movedis detected by a distance encoder 32 and the detected distance isprovided to the camera microcomputer 30 via the lens microcomputer 33.

[0051] (3) Flash control

[0052] The camera microcomputer 30 calculates gain settings at theamplifiers each corresponding to one of the areas S1˜S5 at the flashmetering unit 22, based upon the photometering values, the aperturevalue, the sensitivity value and the distance value described above, thebounced state at the flash light emitting unit 36 and the like. Then,the camera microcomputer 30 sets the gains for the amplifiers in theflash metering unit 22. Once the gains are set, the camera microcomputer30 engages the flash light emitting unit 36 in a preliminary lightemission through the electronic flash microcomputer 35 at the electronicflash device 53. During this process, the flash metering unit 22 storesthe photocurrents corresponding to the quantity of reflected light fromthe subject. The camera microcomputer 30 calculates an instruction valuefor the main light emission quantity based upon the integrated valueobtained at the flash metering unit 22 and outputs the instruction valuethus calculated to the electronic flash microcomputer 35.

[0053] The electronic flash microcomputer 35 calculates the main lightemission quantity based upon the main light emission quantityinstruction value input thereto and the preliminary light emission valuedetected by a light emission monitor unit 37 provided at the electronicflash device 53. The electronic flash microcomputer 35 then engages theflash light emitting unit 36 in the main light emission in response to alight emission trigger signal (X signal) provided by the cameramicrocomputer 30. The electronic flash microcomputer 35 controls themain light emission quantity based upon the integrated value obtainedthrough main light emission integration performed at the light emissionmonitor unit 37 and the main light emission quantity that has beencalculated. The camera microcomputer 30 and the electronic flashmicrocomputer 35 engages in operation together as a preliminary lightemission executing unit.

[0054] As described above, the camera mounted with the electronic flashcontrolling device according to the present invention performs apreliminary light emission in order to ascertain the state of thephotographic field prior to the main light emission by the flash lightemitting unit 36 during a photographing operation. The preliminary lightemission may be achieved either through a single light emission in whicha small quantity of light is emitted compared to the main light emissionquantity, or through several small light emissions repeated over a smalllength of time at a predetermined light emission quantity. In theembodiment, the preliminary light emission is achieved through severalsmall light emissions are repeated over short intervals.

[0055] The light quantity GNp1 per small light emission performed duringthe preliminary light emission and the maximum main light emissionquantity, i.e., the light quantity GNh achieved through a full lightemission normally vary depending upon the type of the electronic flashdevice 53 mounted at the camera main body 51. Thus, if a preliminarylight emission is performed with the maximum number of small lightemissions set at a fixed value regardless of the type of electronicflash device mounted at the camera main body 51, the main light emissionmay become disabled or a sufficient quantity of light may not theemitted during the main light emission.

[0056] For instance, when there are two electronic flash devices withthe light quantities GNp1 per small light emission equal to each otherbut different maximum main light emission quantities GNh from eachother, a larger onus is placed on the electronic flash device with thesmaller maximum main light emission quantity GNh during the preliminarylight emission. In other words, when preliminary light emissions areperformed by the two electronic flash devices through a given number ofsmall light emissions, the ratio of the preliminary light emissionquantity to the entire light emission quantity is larger in theelectronic flash device with the smaller maximum main light emissionquantity GNh than in the electronic flash device with the larger maximummain light emission quantity GNh. As a result, a smaller quantity ofenergy will be left for the main light emission in the electronic flashdevice with the smaller maximum main light emission quantity GNh. If, onthe other hand, the two electronic flash devices have maximum main lightemission quantities GNh equal to each other, the electronic flash devicewith the larger light quantity GNp1 per small light emission will beleft with a smaller quantity of energy available for the main lightemission.

[0057] Accordingly, in order to ensure that the absolute minimum energyrequired for the main light emission is left, the upper limit Qpre_maxto the number of small light emissions performed during the preliminarylight emission should be varied in conformance to the characteristics ofthe electronic flash device in use.

[0058] In the electronic flash controlling device according to thepresent invention, the upper limit to the number of small lightemissions, i.e., the maximum light emission quantity for the preliminarylight emission, is adjusted in conformance to the characteristics of theelectronic flash device 53 mounted at the camera main body 51. Thefollowing is a detailed explanation of the method employed to calculatethe upper limit Qpre_max to the number of small light emissions.

[0059] Information indicating the maximum main light emission quantityGNh and the light emission quantity GNp1 per small light emission at theelectronic flash device 53 is provided to the camera microcomputer 30 atthe camera main body 51 from the electronic flash microcomputer 35 ofthe electronic flash device 53. The upper limit Qpre_max to the numberof small light emissions is calculated at a maximum preliminary lightemission quantity setting unit (not shown) provided at the cameramicrocomputer 30.

[0060] The total light emission quantity Gt when n light emissions havebeen performed with a guide number GNp1 is calculated through thefollowing formula

Gt=GNp1×{square root}{square root over (n)}  (expression 1)

[0061] However, the quantity of energy consumed through this processcannot be determined through (expression 1), presumably because it doesnot incorporate the quantity of energy expended in generating a triggerfor causing the electronic flash device to emit light or the lightemission efficiency corresponding to the light emission quantity. Forthis reason, when attempting to allocate a specific quantity of energyfor the preliminary light emission in an electronic flash device with apredetermined maximum main light emission quantity GNh and apredetermined small light emission quantity GNp1, it is difficult tocalculate the optimal upper limit Qpre_max to the number of small lightemissions through an energy conversion formula such as that presented in(expression 1). Accordingly, the optimal upper limit Qpre_max to thenumber of small light emissions is calculated in the embodiment throughan approximation which conforms to the values obtained through testing.

[0062] Examples of such an approximation are presented in (expression 2)and (expression 3).

Qpre_max=GNh / GNp1  (expression 2)

Qpre _(—) max=Hgn−Pgn−30  (expression 3)

[0063] In the expression above, Hgn=12×log2 (GNh) and Pgn =12×log2(GNp1). It is to be noted that log2 () is a function which assumes alogarithm, the base of which is 2 in ( ).

[0064]FIG. 6 shows the relationships of the maximum main light emissionquantity GNh to the optimal upper limits Qpre_max to the number of smalllight emissions calculated through (expression 2) and (expression 3). Asshown in FIG. 6, the optimal upper limit Qpre_max to the number of smalllight emissions increases as the maximum main light emission quantityGNh increases, regardless of whether the approximation in (expression 2)or (expression 3) is used. It is to be noted that the upper limitQpre_max to the number of small light emissions calculated through thisprocess is a value which does not include the number of blank shots madeat the flash light emitting unit 36.

[0065] (expression 3) represents an example of a relatively simpleapproximation through which the upper limit Qpre_max to the number ofsmall light emissions may be calculated by providing the maximum mainlight emission quantity GNh and the light emission quantity GNp1 persmall light emission at the electronic flash device 53 from theelectronic flash microcomputer 35 to the camera microcomputer 30 as Hgnand Pgn respectively. It is to be noted that the approximation used tocalculate the optimal upper limit Qpre_max to the number of small lightemissions is not limited to (expression 2) or (expression 3) givenabove, and any appropriate approximation that conforms to valuesobtained through testing may be used.

[0066] As explained above, the electronic flash controlling device inthe embodiment calculates the upper limit Qpre_max to the number ofsmall light emissions performed during the preliminary light emissionthrough an approximation and implements preliminary light emissioncontrol accordingly.

[0067] Next, a flash photographing operation performed in a cameramounted with the electronic flash controlling device in the embodimentis explained.

[0068] First, a detailed explanation is given on the flash metering unit22 that meters reflected light from the photographic field during thepreliminary light emission at the electronic flash device 53. FIG. 7illustrates the integrated circuit (hereafter referred to as an IC)achieved at the flash metering unit 22 and the terminals provided at theIC.

[0069] As shown in FIG. 7, external capacitors C1˜C5 that respectivelystore the photocurrents in the five photometering areas S1˜S5 shown inFIG. 5 and an external capacitor SC that adds the photocurrents in theareas S1˜S5 together and stores the total photocurrent in order tooutput a stop signal for stopping the preliminary light emission areconnected to the IC at the flash metering unit 22. Vref indicates atemperature-proportionate voltage terminal and stop indicates a stopsignal output terminal. CSR, CSG and CLK are terminals used to switchbetween the channel setting for setting amplifier gains for theindividual areas S1˜S5 and the channel setting for reading out thephotocurrents having been stored in the capacitors C1˜C5. IS indicates aterminal through which control is implemented to start/end storing thephotocurrents in the capacitors C1˜C5 and SC, DA indicates a terminalthrough which the amplifier gains calculated by the camera microcomputer30 in correspondence to the individual areas S1˜S5 are input as analogvoltages and AD indicates an output terminal through which integratedphotometering values corresponding to the areas S1˜S5 having been storedin the capacitors C1˜C5 respectively are read out. It is to be notedthat these terminals are connected to the camera microcomputer 30.

[0070]FIG. 8 shows the method of setting the amplifier gains for thesignals output from the areas S1˜S5 at the flash metering unit 22. Theterminals CSR, CSG and CLK are each controlled by the cameramicrocomputer 30 so as to set the signal levels. The CSR terminal is setto low level (L level) while sustaining the CSG terminal at high level(H level). Then, as a clock signal is input to the CLK terminal, achannel among Ch1˜Ch5 is selected in synchronization to a fall of theCLK terminal to L level.

[0071] While the CLK terminal is at L level, i.e., while a given channelis selected, a gain for the channel is set by setting the DA terminal tothe voltage level corresponding to the amplifier gain. It is to be notedthat the channels Ch1˜Ch5 respectively correspond to the areas S1˜S5.The method employed to calculate the amplifier gains for the areas S1˜S5at the camera microcomputer 30 is to be detailed later.

[0072]FIG. 9 shows the method of reading out the integratedphotometering values corresponding to the individual areas S1˜S5 at theflash metering unit 22. The CSR terminal and the CSG terminal are set toL level. Then, a channel among Ch1˜Ch5 is selected in synchronizationwith a fall of the CLK terminal to L level by inputting a clock signalto the CLK terminal. During this process, the integrated photometeringvalues from the individual areas S1˜S5 corresponding to the channelsCh1˜Ch5 are output to the AD terminal as voltage levels reflecting theindividual integrated photometering values. The integrated photometeringvalues are transmitted to the camera microcomputer 30 from the ADterminal.

[0073]FIG. 10 is provided to facilitate an explanation of the lightemitting operation performed at the electronic flash controlling devicein the embodiment. The light emitting operation in this figure roughlycorresponds to steps S113 ˜S124 in the flowchart provided in FIG. 17,which is to be explained in detail later.

[0074] As a shutter release signal is input to the camera microcomputer30 by pressing the shutter release switch 26 all the way down and theconstriction of the aperture 10 is completed, gains are set (gainsetting 1) at the flash metering unit 22. At this time, control isimplemented on the CSR terminal, the CSG terminal, the CLK terminal andthe DA terminal as shown in FIG. 8 to set amplifier gains for thesignals output from the individual areas S1˜S5. Following the gainsetting 1, two blank shots are performed at the flash light emittingunit 36 by emitting a small quantity of light in order to warm up theflash light emitting unit 36 and the flash metering unit 22. After thetwo blank shots, the IS terminal is set to L level and a preliminarylight emission is performed at the flash light emitting unit 36 throughrepeated small light emissions and, at the same time, storage ofphotocurrents (preliminary light emission integration) in the capacitorsC1˜C5 and SC at the flash metering unit 22 starts. It is to be notedthat the small light emissions for the blank shots and the preliminarylight emission are performed in response to an input of a clock signalto a communication line (hereafter referred to as an RDY terminal) thatconnects the camera microcomputer 30 to the electronic flashmicrocomputer 35.

[0075] The preliminary light emission ends once a stop signal is outputafter the integrated photometering value at the capacitor SC whichstores the total of the photocurrents in the areas S1˜S5 reaches anappropriate level or after the number of small light emissions reachesthe upper limit Qpre_max explained earlier. The CSR terminal, the CSGterminal, the CLK terminal and the AD terminal are controlled as shownin FIG. 9 to read out the integrated photometering values correspondingto the individual areas S1˜S5 (read-out 1). Then, the IS terminal isturned up to H level to reset the individual integrated values.

[0076] It is to be noted that an integrated value obtained through thepreliminary light emission includes the quantity of light attributableto the ambient light as well as the quantity of reflected lightresulting from the preliminary light emission. Accordingly, anintegration operation is performed exclusively for the ambient lightafter the preliminary light emission is completed as described below,and then the ambient light component is subtracted from the integratedpreliminary light emission value through arithmetic processingsubsequently executed at the camera microcomputer 30 to calculate theintegrated value corresponding to the preliminary light emission alone.

[0077] When the level of the stop signal rises to H level, gains are set(gain setting 2) at the ambient light metering unit 21 in order toperform ambient light integration. Then, as in the preliminary lightemission, the IS terminal is turned down to L level and an integrationoperation (ambient light integration) is executed. At this time, theamplifier gains at the ambient light metering unit 21 are set equal tothe amplifier gains at the flash metering unit 22 set through the gainsetting 1, and the length of time over which the ambient light is to beintegrated “ttei” is set equal to the length of time over which thelight emitted through the preliminary light emission was integrated“tpre”. Once the ambient light integration is completed, the integratedvalues corresponding to the individual areas B1˜B5 are read out(read-out 2), and the integrated values are then reset by turning up theIS terminal to H level.

[0078] The main light emission quantity is calculated based upon analgorithm to be detailed later, a main light emission is executed bycontrolling the flash light emitting unit 36 based upon the calculatedmain light emission quantity during the photographing operation, andthen the photographing operation ends.

[0079]FIG. 11 is provided to facilitate an explanation of the lightemission operation performed at the electronic flash controlling devicewhen the preliminary light emission is executed again. In FIG. 11, apreliminary light emission integration starts as in FIG. 10 after makingtwo blank shots following the gain setting 1. However, the integratedpreliminary light emission value increases drastically after a singlesmall light emission in FIG. 11, which results in an output of a stopsignal to end the preliminary light emission. This may be caused by, forinstance, the presence of a mirror or the like with a high reflectancein the photographic field. Since sufficient information on photographicfield cannot be obtained in such a case amplifier gains are set again atthe flash metering unit 22 (gain setting 2) to re-execute a preliminarylight emission. The re-execution of the preliminary light emission andthe method of setting the gains for the second preliminary lightemission are to be detailed later.

[0080] The amplifier gains set at the flash metering unit 22 arecalculated in correspondence to the individual areas S1˜S5 by the cameramicrocomputer 30 based upon gain calculation command values GaV(i)calculated through the formula presented in (expression 4) below.

GaV(i)=SvV+GnV+XmV+AvV+BvV(i)+BoV+ReV−Sa(i) (i=1˜5)  (expression 4)

[0081] The unit of the gain calculation command values GaV(i) is EV. Thevalues 1˜5 assumed for i correspond to the areas S1˜S5 respectively. Asthe value of a gain calculation command value GaV(i) calculated through(expression 4) increases, a higher gain is set at the flash meteringunit 22. The following is an explanation of parameters used to calculatethe gain calculation command values GaV(i), given in reference to FIGS.12 through 16.

[0082] SvV represents the extent of change attributable to thesensitivity setting at the image-capturing element 12. As shown in FIG.12, SvV increases as the sensitivity SV of the image-capturing element12 rises. As a result, the gain calculation command value GaV(i), too,increases, since the distance over which correct exposure can beachieved extends further as the sensitivity SV at the image-capturingelement 12 becomes higher, it becomes necessary to execute thepreliminary light emission metering operation over a longer distance.However, as it is possible that a photographing operation is performedover a small distance even when the sensitivity SV is high, the extentof change in SvV is adjusted so as to not exceed 1 EV in correspondenceto a change of 1 EV in the sensitivity SV to ensure that the sensitivityis not raised to an excessive degree.

[0083] GnV represents the extent of change attributable to the lightemission quantity GNpl per small light emission. The quantity of lightGNp1 generated through a small light emission changes depending upon thetype of the electronic flash device 53 in use and the angle of flashlight distribution. For this reason, GnV is set so as to achieve aconstant photometering value regardless of the state of the electronicflash device 53. As shown in FIG. 13, GnV is set so that its value isreduced by 1 EV as the small light emission quantity GNp1 increases by 1EV.

[0084] XmV is the extent of change occurring in correspondence to achange in the distance. XmV is set so as to achieve a constantphotometering value regardless of the distance to the subject. As shownin FIG. 14, XmV is set so as to achieve an increase of 1 EV as thedistance increases by an extent corresponding to 1 EV (to a distancemultiplied by a factor of {square root}{square root over (2)}).

[0085] AvV represents the extent of the change attributable to theaperture value. AvV is set so as to achieve a constant photometeringvalue at any aperture value. As shown in FIG. 15, AvV is set so that itincreases by 1 EV as the aperture value increases by an extentcorresponding to 1 EV (as the degree of darkness increases).

[0086] BvV(i) represents the extent of change attributable to thebrightness value. When the brightness of the ambient light increases,the ambient light may enter the flash metering unit 22 during thepreliminary light emission to result in an output of a stop signal toend the integration operation before the integrated values of thereflected light resulting from the flash light generation are fullystored. For this reason, if the brightness BV of the ambient light ishigh, the gain calculation command value GaV(i) for the area where thebrightness BV originates is set low. As shown in FIG. 16, BvV(i) islowered by 1 EV as the brightness BV(i) increases by 1 EV once thebrightness BV(i) exceeds a predetermined value BVofset. When thebrightness BV(i) further increases and BVv(i) is lowered to a specificvalue BvVmax, BvV(i) becomes fixed at BvVmax.

[0087] BoV is a value which is varied depending upon whether or not theflash light is in a bounced state. In a normal state, i.e., if the flashlight is not bounced, BoV is set to 0, whereas if the flash light isbounced, BoV is set to +2EV. When the flash light is bounced, thesubject is illuminated via a ceiling or the like, and thus, the quantityof reflected light from the subject is reduced. For this reason, thegain calculation command value GaV(i) is raised in a bounced state.

[0088] ReV is a value which is varied depending upon whether or not thepreliminary light emission is to be re-executed. ReV is set to 0 for afirst preliminary light emission. If it is decided that the preliminarylight emission must be re-executed as explained later, −3EV, forinstance, is set for ReV to execute the second preliminary lightemission at lowered gain settings.

[0089] Sa(i) represents a correction value which is calculated incorrespondence to the type of the photographic lens 1 and the aperturevalue setting. The correction value Sa(i) is calculated for each of theareas S1˜S5 by using a formula set in advance through testing or thelike.

[0090]FIG. 17 presents a flowchart of the control procedure executed inconformance to a flash photographing control program in the cameramicrocomputer 30 of the electronic flash controlling device in theembodiment of the present invention. The following is an explanation ofthe flash photographing control achieved in the camera microcomputer 30,given in reference to the flowchart in FIG. 17. The program is startedup when the shutter release switch 26 at the camera main body 51 ispressed halfway down. At this point, a halfway press timer (not shown)is activated.

[0091] In step S101, the various settings (the sensitivity, thephotometering mode, the exposure mode and the like) at the camera areread out. In step S102, the focal length, the open aperture, the exitpupil distance, the distance data and the like with regard to thephotographic lens are read out from the lens microcomputer 33 throughlens communication. In step S103, the quantity of light GNp1 emittedthrough a single small light emission during the preliminary lightemission, the maximum main light emission quantity GNh, the state of theflash light emitting unit 36 (whether or not the flash light is in abounced state) and the like are read out through electronic flash devicecommunication. In addition, the upper limit Qpre_max to the number ofsmall light emissions for the preliminary light emission is calculatedas explained earlier based upon the small light emission quantity GNp1and the maximum main light emission quantity GNh.

[0092] In step S104, the ambient light metering unit 21 is engaged in anambient light metering operation to calculate the photometering valuesfor the areas B1˜B5 and the like. In the following step S105, a correctexposure value Bvans is calculated through a method of the known artbased upon the photometering values calculated in step S104 and theaperture value and the shutter speed are calculated in correspondence tothe exposure mode setting.

[0093] In step S106, the focal point detection unit 23 is engaged infocal appoint detection in each of the focal point detection areasF1˜F5. In step S107, the lens optical system 31 is driven so as to setthe defocus quantity to 0 and achieve a focused state in a selectedfocal point detection area by controlling the lens drive unit 24 inconformance to the focal point detection state obtained in step S106. Instep S108, the value representing the distance over which the lensoptical system has moved, which has been detected by the distanceencoder 32 and is regarded as the subject distance, is read out from thelens microcomputer 33.

[0094] In step S109, a decision is judged as to whether or not theshutter release switch 26 has been pressed all the way down. If anaffirmative judgement is made in step S109, the operation proceeds tostep S110. If, on the other hand, a negative judgement is made in stepS109, the operation proceeds to step S126. In step S110, the main mirror2 is allowed to swing upward and, at the same time, the aperture 10 isconstricted.

[0095] In step S111, 0 is set fora flag FLG_PRE which indicates apreliminary light emission is to be re-executed. In step S112, the gaincalculation command values GaV(i) for the individual areas S1˜S5 at theflash metering unit 22 are calculated through (expression 4) explainedearlier. In step S113, a preliminary light emission is executed byengaging the electronic flash device 53. The preliminary light emissionoperation is to be explained in detail later in reference to theflowchart presented in FIG. 18.

[0096] In step S114, an arithmetic operation is performed forpreliminary light emission re-execution decision-making, based upon thephotometering values obtained at the flash metering unit 22. Thepreliminary light emission is re-executed if the preliminary lightemission following the blank shots stops after a single small lightemission and any of the integrated values IGpre(i) corresponding to theareas S1˜S5 at the flash metering unit 22 has reached a saturation levelstored in memory in advance. In step 115, a decision is judged as towhether or not the preliminary light emission is to be re-executed. Ifan affirmative judgement is made in step S115 and the preliminary lightemission is to be re-executed, the operation proceeds to step S116. If,on the other hand, a negative judgement is made in step S115, theoperation proceeds to step S118.

[0097] In step S116, 1 is set for the flag FLG_PRE that indicates thepreliminary light emission is to be re-executed. In step S117, −3 is setfor the parameter ReV used to calculate the gain calculation commandvalues GaV(i), then the operation returns to stepped S112 to recalculatethe gain calculation command values GaV(i).

[0098] In step S118, the ambient light metering unit 21 is engaged in anambient light integration operation and the integrated values IGtei(i)are read out. The ambient light integration operation is performed withgains set the same as those for the preliminary light emissionintegration operation and over the same length of operating time as thatfor the preliminary light emission integration operation. Namely,tpre=ttei in FIG. 10 and tpre2=ttei in FIG. 11.

[0099] In step S119, GV(i) (i=1˜5) for the individual flash controlareas S1˜S5 are calculated based upon the integrated values obtainedthrough the preliminary light emission and the like. Each GV(i)represents a variable related to the subject reflectance in one of theareas S1˜S5. The unit of GV(i) is EV. GV(i) is calculated through thefollowing formula in (expression 5).

GV(i)=log2 (GNp1)+log2(Qpre)+GaV(i)+log2(IGstop/IG(i))+Gofset  (expression 5)

[0100] In the expression above, Qpre represents the number of smalllight emissions performed in the preliminary light emission, whichexcludes the number of blank shots, and GaV(i) represents the gaincalculation command values in the corresponding area among the areasS1˜S5 calculated through (expression 4) In addition, IGstop representsthe theoretical value of IG(i) taken when the stop signal is output.Gofset represents the offset value. It is to be noted that as expressedin (expression 6), IG(i) is obtained by subtracting the ambient lightintegrated value IGtei in a given area from the corresponding integratedpreliminary light emission value IGpre(i).

IG(i)=IGpre(i)−IGtei(i) (IG(i)>0)  (expression 6)

[0101] In the following step s120, weights wt(i) for the individualareas S1˜S5 and a level correction value ΔY are calculated through amethod to be explained later, based upon the results of the calculationof GV(i) performed in step S119 and the like. The weights wt(i) and thelevel correction value ΔY are to be detailed later.

[0102] In step S121, a main light emission quantity instruction valuekgn to be used when calculating the light emission quantity for the mainlight emission is calculated through the following formula in(expression 7).

kgn=ΔY−log2 (GNp1)−log2 (Qpre)−log2 (Σ(wt(i) /2^(GV(i)))+C  (expression7)

[0103] In the expression above, C represents the offset value.

[0104] In step S122, the main light emission quantity instruction valuekgn calculated in step S121 and the number of invalid small lightemissions stn is provided to the electronic flash microcomputer 35through communication.

[0105] The number of invalid small light emissions stn equals the numberof blank shots (2) if it was judged in step S115 that the preliminarylight emission was not to be re-executed. If, on the other hand, it wasjudged in step S115 that the preliminary light emission was to bere-executed and consequently, the preliminary light emission has beenre-executed, the number of invalid small light emissions equals the sumof the number of blank shots (2) and the first small light emission (1).It is to be noted that the electronic flash microcomputer 35 calculatesthe main light emission quantity for the main light emission to beperformed by the light emitting unit 36 based upon the main lightemission quantity instruction value kgn, the number of invalid smalllight emissions stn and the like input thereto.

[0106] In the following step S123, the shutter 11 is released. In stepS124, the exposure control is implemented by controlling the shutterspeed and a subject image is formed at the image-capturing element 12.Concurrently, the electronic flash microcomputer 35 implements lightemission quantity control for the main light emission by the flash lightemitting unit 36.

[0107] In step 125, the shutter 11, the aperture 10 and the main mirror2 are reset to their initial positions. In step S126, a decision isjudged as to whether or not apredetermined length of time has elapsedafter activating the halfway press timer. If a negative judgement ismade in step S126 i.e., the predetermined length of time has not yetelapsed, the operation returns to step S101 to repeat the processing,whereas if an affirmative judgement is made, the processing ends.

[0108]FIG. 18 presents a flowchart of the subroutine executed in thecontrol procedure implemented in conformance to the flash photographingcontrol program by the camera microcomputer 30 as shown in the flowchartin FIG. 17. The flowchart in FIG. 18 shows the method employed toimplement the preliminary light emission in step S113 in FIG. 17.

[0109] In step S201, gains DApre(i) to be actually set at the amplifiersof the flash metering unit 22 are calculated through the formula in(expression 8) below by using the gain calculation command values GaV(i)calculated in step S112 as explained earlier.

DApre(i)=(pre_level(i)−GaV(i)×pre_gamma)×T/Tref(i=1˜5)  (expression 8)

[0110] In the expression above, pre_level(i) represents a predeterminedreference value of the preliminary light emission flash control leveland pre_gamma represents the gamma adjustment value. T represents thecurrent temperature and Tref represents the temperature set in advancefor the adjustment. It is to be noted that since an amplifier gainsetting becomes higher as the voltage at the DA terminal of the flashmetering unit 22 becomes lower, GaV(i)×pre_gamma is subtracted frompre_level in (expression 8). The gains DApre thus calculated are set atthe flash metering unit 22 through the method shown in FIG. 8.

[0111] In step S202 the flash light emitting unit 36 makes two blankshots. In step S203, a time count for the length of time Tpre over whichthe preliminary light emission integration operation is to be performedstarts. At the same time, the IS terminal at the flash metering unit 22is lowered to L level, thereby starting the preliminary light emissionintegration operation. In step S204, 0 is set for the variable Qprerepresenting the number of small light emissions performed in thepreliminary light emission. Qpre indicates the number of small lightemissions which does not include the number of blank shots.

[0112] In step S205, 1 is added to the number of small light emissionsQpre. In step S206, the flash light emitting unit 36 is engaged in asmall light emission at the light emission quantity GNp1. In step S207,a decision is judged as to whether or not a stop signal has been output.If an affirmative judgement is made in step S207 that a stop signal hasbeen output, the operation proceeds to step S209. If, on the other hand,a negative judgement is made in step S207, the operation proceeds tostep S208.

[0113] In step S208, a decision is judged as to whether or not thenumber of small light emissions Qpre has reached the preset upper limitQpre_max. If a negative judgement is made in step S208, the operationreturns to step S205.

[0114] In step S209, the time count for the length of time tpre for thepreliminary light emission integration operation ends. In step S210, theintegrated preliminary light emission values IGpre (I) for theindividual areas S1˜S5 are read out through the method shown in FIG. 9and stored. Then, the operation makes a return.

[0115] It is to be noted that in the preliminary light emissionoperation in the flowchart in FIG. 18 explained above, the preliminarylight emission is not re-executed. If it is judged in step S115 in FIG.17 that the preliminary light emission is to be re-executed, theprocessing in steps S202 and S204 in FIG. 18 is skipped when performingthe second preliminary light emission. In other words, when executingthe second preliminary light emission, the number of small lightemissions performed in the second preliminary light emission is added tothe number of small light emissions performed in the first preliminarylight emission in step S205 to use the sum as the number of small lightemissions Qpre.

[0116] Next, the main light emission control implemented by theelectronic flash controlling device in the embodiment is explained inreference to FIG. 19. The main light emission is controlled by theelectronic flash microcomputer 35 of the electronic flash device 53.FIG. 19 presents a flowchart of the processing procedure executed forthe main light emission control in the electronic flash microcomputer35.

[0117] In step S301, a decision is judged as to whether or not the mainlight emission quantity instruction value kgn for calculating the mainlight emission quantity and the number of invalid small light emissionsstn have been provided through communication with the cameramicrocomputer 30. This processing corresponds to the processingperformed in step S122 in FIG. 17.

[0118] If an affirmative judgement is made in step S301, the operationproceeds to step S302 for a flash control mode 1 to calculate the mainlight emission quantity through a method of the known art. If, on theother hand, it is judged in step S301 that no communication has beenperformed from the camera microcomputer 30, the operation proceeds tostep S303. In step S303, an external flash control mode (flash controlmode 2) is set at the electronic flash device 53.

[0119] In step S304, a decision is judged as to whether or not a lightemission trigger signal (X signal) has been output. If an affirmativejudgement is made in step S304, the operation proceeds to step S305. Ifa negative judgement is made in step S304, on the other hand, theoperation returns to step S301.

[0120] In step S305, the main light emission is performed in theselected mode. It is tobe noted that if the flash control mode 1 hasbeen selected, the electronic flash microcomputer 35 stops the lightemission once the quantity of light emitted by the flash light emittingunit 36, which is detected by the light emissionmonitor unit 37 reachesthe main light emission quantity that has been calculated. If the flashcontrol mode 2, i.e., the external flash control mode, has beenselected, on the other hand, the electronic flash microcomputer 35employs a sensor (not shown) internally provided at the electronic flashdevice 53 to detect the reflected light from the subject and stops thelight emission once the level of the reflected light reaches apredetermined value.

[0121] Next, a brief explanation is given on the method employed tocalculate the weights wt(i) and the level correction quantity (the flashcontrol correction quantity) ΔY in step S120 in FIG. 17.

[0122] First, the subject reflectances RefEV(i) corresponding to theindividual areas S1˜S5 are calculated using GV(i) in the areas S1˜S5calculated through (expression 5) as explained earlier, in order tocalculate the weights wt(i) and the level correction quantity ΔY.

RefEV(i)=2×X+AV−GV (i) (i=1˜5)  (expression 9)

[0123] X represents the photographing distance (unit: m) and AVrepresents the photographic aperture value (unit: AV). It is to be notedthat the photographing distance X may be calculated based upon, forinstance, the distance over which the lens optical system 31 has moved,which is detected by the distance encoder 32 at the lens main body 52.

[0124] The subject reflectances RefEV(i) are each a variable that is setto 0 if the reflectance equals a standard value, that is set to +1 ifthe reflectance is higher by 1 level (+1 level) relative to the standardvalue, that is set to −1 if the reflectance is lower by 1 level (−1level) relative to the standard value and so forth.

[0125] Using the subject reflectances RefEV(i) calculated through(expression 9), weighting values RefG(i) for the individual areas S1˜S5are calculated in correspondence to their reflectances.

RefG(i)=1/(2^(Abs(RefEV(i)))) (i=1˜5)  (expression 10)

[0126] Abs( ) is a function that determines the absolute number within (). As shown in FIG. 20, a weighting value RefG(i) is 1 if the subjectreflectance RefEV(i) equals the standard value (0). In addition, theweighting value RefEV(i) becomes smaller as the subject reflectanceRefEV(i) deviates further away from the standard value (0).

[0127] The weights wt(i) for the areas S1˜S5 are individually calculatedas expressed below, using the weighting values RefG(i).

wt(i)=RefG(i) /Σ(RefG(i)) (i=1˜5)  (expression 11)

[0128] A reflectance correction value Ref (Main) for the entirephotographic field is calculated using RefEV(i) calculated through(expression 9) and the weights wt(i) calculated through (expression 11).

Ref (Main) log2 (Σ(wt (i)×2^(RefEV(i)))) (i=1˜5)  (expression 12)

[0129] Using the reflectance correction value Ref (Main) thuscalculated, the main light emission quantity correction value ΔY is nowcalculated through the following formula.

ΔY=krm×Ref(Main)  (expression 13)

[0130] krm represents a constant used to adjust the correction extentRef(Main) of the subject reflectance. For instance, krm may be set toapproximately 0.5. krm may be a value that can be varied as necessary.FIG. 21 shows the relationship between the subject reflectance and themain light emission quantity correction value ΔY. As shown in FIG. 21,an increase in the reflectance results in an increase in the main lightemission quantity correction value ΔY.

[0131] As explained above, the electronic flash controlling deviceaccording to the present invention sets the maximum light emissionquantity for the preliminary light emission in correspondence to thetype of the electronic flash device 53 mounted at the camera main body51. In more specific terms, the upper limit Qpre_max to the number ofsmall light emissions performed in the preliminary light emission is setin conformance to the type of the electronic flash device 53. The upperlimit Qpre_max to the number of small light emissions is calculatedbased upon the maximum main light emission quantity GNh and the lightemission quantity GNp1 per small light emission that are inherent to agiven electronic flash device 53. Since control is implemented duringthe preliminary light emission by ensuring that the number of smalllight emissions does not exceed the upper limit Qpre_max, it is possibleto assure a sufficient light emission quantity for the main lightemission even as the required photographic field information is obtainedthrough the preliminary light emission. Even when the preliminary lightemission is re-executed due to the presence of a mirror or the like witha high reflectance in the photographic field, control is achieved so asto ensure that the total number of small light emissions does not exceedthe upper limit Qpre_max.

[0132] Thus, particularly , even when an electronic flash device 53 witha small maximum main light emission quantity is mounted, a preliminarylight emission can be performed while assuring a sufficient lightemission quantity for the main light emission.

Variations of the Embodiment

[0133] The maximum light emission quantity for the preliminary lightemission may be set in advance at a preliminary light emissionregulating unit (not shown) at the electronic flash microcomputer 35 ofthe electronic flash device 53 in the electronic flash controllingdevice according to the present invention. The preliminary lightemission regulating unit regulates the actual quantity of light emittedfor the preliminary light emission by the flash light emitting unit 36,i.e., the upper limit to the number of small light emissions performedfor the preliminary light emission in this example, in response to aninstruction for the preliminary light emission issued by the cameramicrocomputer 30.

[0134]FIG. 22 presents a flowchart of the processing procedureimplemented during the preliminary light emission control by theelectronic flash microcomputer 35 in a variation of the embodiment.QpreSB represents the number of small light emissions counted by theelectronic flash microcomputer 35. QpreSB_max represents the upper limitto the number of small light emissions set in advance at the preliminarylight emission regulating unit of the electronic flash microcomputer 35.

[0135] In step S401 following the two blank shots, 0 is set for thenumber of small light emissions QpreSB. In step S402, a decision isjudged as to whether or not an RDY signal for enabling a small lightemission has been input from the camera microcomputer 30. If anaffirmative judgement is made in step S402, the operation proceeds tostep S403. In step S403, 1 is added to QpreSB. In step S404, the flashlight emitting unit 36 is engaged in a small light emission performed atthe guide number GNp1.

[0136] In step S405, a decision is judged as to whether or not thenumber of small light emissions QpreSB is equal to or higher than thepreset upper limit QpreSB_max. If an affirmative judgement is made instep S405, i.e., if the number of small light emissions QpreSB is equalto or larger than the upper limit QpreSB_max, no more small lightemission is performed. If, on the hand, a negative judgement is made instep S405, the operation returns to step S402.

[0137] As explained above, an advantage similar to that realized in theembodiment is achieved by setting in advance the upper limit QpreSB_maxto the number of small light emissions, i.e., the maximum light emissionquantity for the preliminary light emission, at the electronic flashmicrocomputer 35 of the electronic flash device 53 as well. If the upperlimit QpreSB_max to the number of small light emissions set at theelectronic flash microcomputer 35 is smaller than the upper limitQpre_max to the number of small light emissions calculated at the cameramicrocomputer 30, the number of small light emissions is limited inconformance to the upper limit QpreSB_max set at the electronic flashmicrocomputer 35. As a result, a sufficient light emission quantity forthe main light emission can be secured with a higher degree ofreliability.

[0138] It is to be noted that if the upper limit Qpre_max to the numberof small light emissions calculated at the camera microcomputer 30 issmaller than the upper limit QpresB_max to the number of small lightemissions set at the electronic flash microcomputer 35, priority isgiven to the upper limit Qpre_max calculated at the camera microcomputer30, since the camera microcomputer 30 does not output an RDY signal oncethe number of small light emissions exceeds the upper limit Qpre_max.

[0139] The upper limit QpreSB_max to the number of small light emissionsset at the electronic flash microcomputer 35 may be varied inconformance to the state of the lens zooming operation or the like.

[0140] While an explanation has been given in reference to theembodiment on an example in which the present invention is adopted in adigital still camera employing an image-capturing element such as a CCD,the present invention may be adopted in a similar manner in conjunctionwith a camera which exposes silver halide film.

[0141] An explanation has been given on an example in which the upperlimit Qpre_max to the number of small light emissions is set when thepreliminary light emission is achieved by repeating small lightemissions. However, the present invention may also be adopted when thepreliminary light emission is achieved through a single light emissionas well. In other words, the present invention may be adopted in anyapplication as long as the maximum preliminary light emission quantityfor the preliminary light emission is calculated based upon the maximummain light emission quantity of a given electronic flash device tosecure a sufficient light emission quantity for the main light emission.

[0142] The above described embodiments are examples, and variousmodifications can be made without departing from the spirit and scope ofthe invention.

What is claimed is:
 1. An electronic flash controlling device employedto control a flash light emitting unit that performs a main lightemission and a preliminary light emission prior to the main lightemission, comprising: a maximum preliminary light emission quantitysetting unit that sets a maximum preliminary light emission quantity forthe preliminary light emission during which a smaller quantity of lightis emitted than a maximum light emission quantity based upon maximumlight emission quantity information regarding a total light emissionquantity which the flash light emitting unit is capable of generating;and a preliminary light emission executing unit that engages the flashlight emitting unit in the preliminary light emission by using themaximum preliminary light emission quantity set by said maximumpreliminary light emission quantity setting unit as an upper limit. 2.An electronic flash controlling device according to claim 1, wherein:said preliminary light emission executing unit engages the flash lightemitting unit to perform small light emissions repeatedly at apredetermined light emission quantity to execute the preliminary lightemission.
 3. An electronic flash controlling device according to claim2, wherein: said maximum preliminary light emission quantity settingunit sets the maximum preliminary light emission quantity for thepreliminary light emission based upon unit light emission quantityinformation regarding a unit light emission quantity for the small lightemissions as well as the maximum light emission quantity information. 4.An electronic flash controlling device according to claim 3, wherein:said maximum preliminary light emission quantity setting unit sets themaximum preliminary light emission quantity by setting an upper limit toa number of small light emissions to be performed repeatedly.
 5. Anelectronic flash controlling device according to claim 3, wherein: saidmaximum preliminary light emission quantity setting unit sets themaximum preliminary light emission quantity based upon a ratio of themaximum light emission quantity information and said unit light emissionquantity information.
 6. A camera having an electronic flash controllingdevice according to claim 1, wherein: said maximum preliminary lightemission quantity setting unit sets the maximum preliminary lightemission quantity by receiving maximum light emission quantityinformation transmitted from an electronic flash device that includesthe flash light emitting unit.
 7. A camera having an electronic flashcontrolling device according to claim 2, wherein: said maximumpreliminary light emission quantity setting unit sets the maximumpreliminary light emission quantity by receiving maximum light emissionquantity information transmitted from an electronic flash device thatincludes the flash light emitting unit.
 8. A camera having an electronicflash controlling device according to claim 3, wherein: said maximumpreliminary light emission quantity setting unit sets the maximumpreliminary light emission quantity by receiving maximum light emissionquantity information and unit light emission quantity informationtransmitted from an electronic flash device that includes the flashlight emitting unit.
 9. A camera having an electronic flash controllingdevice according to claim 4, wherein: said maximum preliminary lightemission quantity setting unit sets the maximum preliminary lightemission quantity by receiving maximum light emission quantityinformation and unit light emission quantity information transmittedfrom an electronic flash device that includes the flash light emittingunit.
 10. A camera having an electronic flash controlling deviceaccording to claim 5, wherein: said maximum preliminary light emissionquantity setting unit sets the maximum preliminary light emissionquantity by receiving maximum light emission quantity information andunit light emission quantity information transmitted from an electronicflash device that includes the flash light emitting unit.
 11. Anelectronic flash controlling system comprising: a camera main bodyhaving a maximum preliminary light emission quantity setting unit thatsets a maximum preliminary light emission quantity for a preliminarylight emission during which a smaller quantity of light is emitted thana maximum light emission quantity, based upon maximum light emissionquantity information regarding a total light emission quantity which aflash light emitting unit is capable of generating, and a preliminarylight emission executing unit that issues an instruction to perform thepreliminary light emission to the flash light emitting unit by using themaximum preliminary light emission quantity set by said maximumpreliminary light emission quantity setting unit as an upper limit; andan electronic flash device that can be detachably mounted at said cameramain body, having said flash light emitting unit that performs a mainlight emission and the preliminary light emission prior to the mainlight emission and a preliminary light emission regulating unit thatregulates said flash light emitting unit to disallow a preliminary lightemission which results in a light emission quantity exceeding apredetermined preliminary light emission quantity even if theinstruction has been issued from said camera main body to perform thepreliminary light emission which results in the light emission quantityexceeding the predetermined preliminary light emission quantity.
 12. Anelectronic flash controlling system according to claim 11, wherein: saidpreliminary light emission executing unit issues an instruction toperform small light emissions repeatedly at a predetermined lightemission quantity to said flash light emitting unit and sets the maximumpreliminary light emission quantity by setting an upper limit to anumber of small light emissions; and said preliminary light emissionregulating unit regulates the small light emissions at said flash lightemitting unit if the upper limit to the number of small light emissionsset by said preliminary light emission executing unit exceeds a numberof preliminary light emissions corresponding to a predeterminedpreliminary light emission quantity.